e of practically the same
average temperature as that which is to be used during the test.
Barrel 3 should be high enough above the feed pump so that the pump
will handle hot water. Put barrel 3 on a scales, before connecting
it to the feed pump, and weigh it. Then let the water from barrel 1
run into barrel 3, and weigh again. The second weight minus the
first weight is the net weight of water run in from barrel 1 and is
the weight of water contained in barrel 1 when filled to the
overflow. The weight of water in barrel 2 when it is filled to the
overflow can be found in like manner. Mark these weights down.

[Illustration: _Fig. 2._]

When the net weights are found and barrel 3 is removed from the
scales and connected to the feed pump, the apparatus is ready to
begin the test. Start with the level of the water about 1 foot
below the top of the barrel 3, and drive a nail into the barrel to
mark this level. When the test is finished, the level should be
brought to the same point, so that the water that has passed
through barrels 1 and 2 will accurately represent the weight of
water fed to the boiler during the test.

When the test is to begin, stop the feed pump and tie a string
around the gage glass on the boiler to mark the height of the water
level in the boiler. Then start the pump connected to barrel 3.
Fill barrels 1 and 2 up to the overflow before the test is started.
Then open the valve _V_ on barrel 1 and let the water run into
barrel 3 as fast as the feed pump draws water from barrel 3. When
barrel 1 is emptied close its valve _V_ and open its valve _A_ so
as to refill it.

While barrel 1 is filling empty barrel 2 into barrel 3 in the same
way, and continue to fill and empty barrels 1 and 2 alternately. In
this way barrel 3 will be kept supplied with water that has been
measured in barrels 1 and 2, the net weights of which were found
before the test began. Keep a separate tally of the number of times
each of the barrels 1 and 2 is emptied into barrel 3. At the end of
the test the number of tallies for each barrel multiplied by the
weight of the water that barrel will hold will be the weight of
water measured in that barrel. The sum of these weights for barrels
1 and 2 will be the weight of water used in the test.

With a three-barrel arrangement like this, water can be weighed
rapidly enough to supply 300 boiler horsepower.

Before starting a test make sure that there is no chance for water
to leak in